An interconnection inverter device according to a conventional technique of this type includes, for example, one that is disclosed in Patent Literature 1 below. The interconnection inverter device disclosed in Patent Literature 1 is configured to include first power conversion unit which has a step-down function and is disposed on the input side of a reactor; second power conversion unit which has a step-up function and is disposed on the output side of the reactor; and third power conversion unit disposed on the output side of the second power conversion unit to convert a direct current to an alternating current and then output the resulting current to an electric power system. The device provides control to switch between the first power conversion unit and the second power conversion unit depending on the system voltage and the magnitude of an input voltage to the first power conversion unit.